/*
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at 
 * 
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *  
 */

using System;
using java = biz.ritter.javapi;

namespace org.apache.commons.collections.keyvalue
{

    /** 
     * A <code>MultiKey</code> allows multiple map keys to be merged together.
     * <p>
     * The purpose of this class is to avoid the need to write code to handle
     * maps of maps. An example might be the need to lookup a filename by 
     * key and locale. The typical solution might be nested maps. This class
     * can be used instead by creating an instance passing in the key and locale.
     * <p>
     * Example usage:
     * <pre>
     * // populate map with data mapping key+locale to localizedText
     * Map map = new HashMap();
     * MultiKey multiKey = new MultiKey(key, locale);
     * map.put(multiKey, localizedText);
     *
     * // later retireve the localized text
     * MultiKey multiKey = new MultiKey(key, locale);
     * String localizedText = (String) map.get(multiKey);
     * </pre>
     * 
     * @since Commons Collections 3.0
     * @version $Revision$ $Date$
     * 
     * @author Howard Lewis Ship
     * @author Stephen Colebourne
     */
    [Serializable]
    public class MultiKey : java.io.Serializable
    {
        // This class could implement List, but that would confuse it's purpose

        /** Serialisation version */
        private static readonly long serialVersionUID = 4465448607415788805L;

        /** The individual keys */
        private Object[] keys;
        /** The cached hashCode */
        private int hashCodeJ;

        /**
         * Constructor taking two keys.
         * <p>
         * The keys should be immutable
         * If they are not then they must not be changed after adding to the MultiKey.
         * 
         * @param key1  the first key
         * @param key2  the second key
         */
        public MultiKey(Object key1, Object key2) :
            this(new Object[] { key1, key2 }, false)
        {
        }

        /**
         * Constructor taking three keys.
         * <p>
         * The keys should be immutable
         * If they are not then they must not be changed after adding to the MultiKey.
         * 
         * @param key1  the first key
         * @param key2  the second key
         * @param key3  the third key
         */
        public MultiKey(Object key1, Object key2, Object key3) :
            this(new Object[] { key1, key2, key3 }, false)
        {
        }

        /**
         * Constructor taking four keys.
         * <p>
         * The keys should be immutable
         * If they are not then they must not be changed after adding to the MultiKey.
         * 
         * @param key1  the first key
         * @param key2  the second key
         * @param key3  the third key
         * @param key4  the fourth key
         */
        public MultiKey(Object key1, Object key2, Object key3, Object key4) :
            this(new Object[] { key1, key2, key3, key4 }, false)
        {
            ;
        }

        /**
         * Constructor taking five keys.
         * <p>
         * The keys should be immutable
         * If they are not then they must not be changed after adding to the MultiKey.
         * 
         * @param key1  the first key
         * @param key2  the second key
         * @param key3  the third key
         * @param key4  the fourth key
         * @param key5  the fifth key
         */
        public MultiKey(Object key1, Object key2, Object key3, Object key4, Object key5) :
            this(new Object[] { key1, key2, key3, key4, key5 }, false)
        {
        }

        /**
         * Constructor taking an array of keys which is cloned.
         * <p>
         * The keys should be immutable
         * If they are not then they must not be changed after adding to the MultiKey.
         * <p>
         * This is equivalent to <code>new MultiKey(keys, true)</code>.
         *
         * @param keys  the array of keys, not null
         * @throws IllegalArgumentException if the key array is null
         */
        public MultiKey(Object[] keys) :
            this(keys, true)
        {
        }

        /**
         * Constructor taking an array of keys, optionally choosing whether to clone.
         * <p>
         * <b>If the array is not cloned, then it must not be modified.</b>
         * <p>
         * This method is public for performance reasons only, to avoid a clone.
         * The hashcode is calculated once here in this method.
         * Therefore, changing the array passed in would not change the hashcode but
         * would change the equals method, which is a bug.
         * <p>
         * This is the only fully safe usage of this constructor, as the object array
         * is never made available in a variable:
         * <pre>
         * new MultiKey(new Object[] {...}, false);
         * </pre>
         * <p>
         * The keys should be immutable
         * If they are not then they must not be changed after adding to the MultiKey.
         *
         * @param keys  the array of keys, not null
         * @param makeClone  true to clone the array, false to assign it
         * @throws IllegalArgumentException if the key array is null
         * @since Commons Collections 3.1
         */
        public MultiKey(Object[] keys, bool makeClone)
            : base()
        {
            if (keys == null)
            {
                throw new java.lang.IllegalArgumentException("The array of keys must not be null");
            }
            if (makeClone)
            {
                this.keys = (Object[])keys.clone();
            }
            else
            {
                this.keys = keys;
            }

            int total = 0;
            for (int i = 0; i < keys.Length; i++)
            {
                if (keys[i] != null)
                {
                    total ^= keys[i].GetHashCode();
                }
            }
            hashCodeJ = total;
        }

        //-----------------------------------------------------------------------
        /**
         * Gets a clone of the array of keys.
         * <p>
         * The keys should be immutable
         * If they are not then they must not be changed.
         * 
         * @return the individual keys
         */
        public Object[] getKeys()
        {
            return (Object[])keys.clone();
        }

        /**
         * Gets the key at the specified index.
         * <p>
         * The key should be immutable.
         * If it is not then it must not be changed.
         * 
         * @param index  the index to retrieve
         * @return the key at the index
         * @throws IndexOutOfBoundsException if the index is invalid
         * @since Commons Collections 3.1
         */
        public Object getKey(int index)
        {
            return keys[index];
        }

        /**
         * Gets the size of the list of keys.
         * 
         * @return the size of the list of keys
         * @since Commons Collections 3.1
         */
        public int size()
        {
            return keys.Length;
        }

        //-----------------------------------------------------------------------
        /**
         * Compares this object to another.
         * <p>
         * To be equal, the other object must be a <code>MultiKey</code> with the
         * same number of keys which are also equal.
         * 
         * @param other  the other object to compare to
         * @return true if equal
         */
        public bool equals(Object other)
        {
            if (other == this)
            {
                return true;
            }
            if (other is MultiKey)
            {
                MultiKey otherMulti = (MultiKey)other;
                return java.util.Arrays<Object>.equals(keys, otherMulti.keys);
            }
            return false;
        }

        /**
         * Gets the combined hash code that is computed from all the keys.
         * <p>
         * This value is computed once and then cached, so elements should not
         * change their hash codes once created (note that this is the same 
         * constraint that would be used if the individual keys elements were
         * themselves {@link java.util.Map Map} keys.
         * 
         * @return the hash code
         */
        public override int GetHashCode()
        {
            return hashCodeJ;
        }

        /**
         * Gets a debugging string version of the key.
         * 
         * @return a debugging string
         */
        public override String ToString()
        {
            return "MultiKey" + java.util.Arrays<Object>.asList(keys).toString();
        }

    }
}